This invention is directed to an apparatus and methods for conveying xe2x80x9cflowablexe2x80x9d materials through a conduit, such as, a pipe or hose, over long distances.
xe2x80x9cFlowablexe2x80x9d materials are those capable of flow movement, such as gases or a combination of gas and solids and/or liquids. Conveying systems for transporting flowable materials, such as pneumatic conveying systems, high and low pressure natural gas pipelines, flow lines, transmission lines, gathering systems, vapor recovery systems, coal bed methane gas lines, and liquid conduits, are known in the art, but all present problems when the materials are to be transported over large distances.
Pneumatic conveying systems for transporting material through a conduit have been in use for years and are well known in the art. Over the years the designs of these systems have changed to provide for greater efficiency in operational cost and labor. For instance, early systems utilized belt driven conveyors to transport materials from an input hopper to a mixing chamber. Unfortunately, these systems were inefficient in that the belt drives experienced many problems, such as wearing and breakage. Due, in part to problems experienced with belt systems, pneumatic conveying systems were developed.
Generally, pneumatic conveying systems include a feed mechanism, such as, an auger, for transporting the material to a mixing chamber. In the mixing chamber, the material is entrained in pressurized air which is supplied into the mixing chamber through jets or air inlets. In some systems, the material and air are mixed and accelerated in an accelerating device, such as, a venturi pipe, which is connected to the mixing chamber. The accelerated mixture is then transported out of the venturi pipe and into a conduit which conveys the materials to a specified destination. Typically, conventional pneumatic conveying systems can transport material up to about 1,000 feet. The limited distance the material can be conveyed is due, in part, to the operating pressure of the system and the instability of the material flow in the conduit.
Many other problems also exist with pneumatic conveying systems. For example, if excessive pressure builds up in the conduit, e.g., from a blockage in the conduit, gas and product back flow into the hopper. This back flow is known as xe2x80x9cblowbackxe2x80x9d. Further, as the material travels through the conveying conduit, in earlier designs, and current designs, it strikes the walls of the conduit. This not only damages the walls of the conduit, but damages the material as well. Thus, problems of erosion of equipment and attrition of product are also present. Finally, many current designs incur a high cost of operation due to the high requirement of energy input to operate the system.
Many pneumatic systems have been developed to address different problems. For instance, the blowback problem, among others, was addressed in the system described in U.S. Pat. No. 4,711,607 to Wynosky et al. In the Wynosky device, a rotating auger enclosed by a cylindrical barrel transports particulate material towards the discharge end of the barrel which resides within a plenum chamber. Pressurized gas is introduced into the plenum chamber for creating a gas flow in a venturi pipe, which is coupled at one end to the plenum chamber and at its other end to a conduit used to transport the material. Measurements of the pressure differential between the plenum chamber and the conduit are used to monitor potential blowback problems. Further, this system operates at lower operating pressures than most systems, e.g., 12-15 psi. Nonetheless, this system does not achieve a sufficiently stable flow of material through the conduit, which restricts the distance over which the material can be transported, including the ability to transport the material through elevational or directional changes.
U.S. Pat. No. 5,681,132 to Sheppard, Jr. describes an on-line pumping unit designed to extend transport distances. In Sheppard, the pumping unit includes a screw conveyor assembly coupled to a laminar flow, inductor assembly. In this system, the inductor assembly forms the core of a linear accelerator apparatus used to extend transport distances. Nonetheless, this system does not teach how material can be conveyed over very long distances, such as, for example, a mile.
Known natural gas conveying systems, pipelines, transmission lines, and gathering systems have similar problems. Gas is conveyed through the natural gas flow line in mid-and high-pressure systems in a turbulent flow. Turbulent flow results in friction loss and energy inefficiency, resulting in increased pressure drop. Therefore, higher pressure, increased compressor size, and increased pipeline capacity is needed to push the quantity of gas through the long distance.
Fluids frequently accumulate in low points of the flow line in high, mid and low pressure systems and these low points therefore sometimes have significantly higher pressure than other portions, resulting in erratic gas production. To alleviate this problem in larger lines, a xe2x80x9cpigxe2x80x9d is used as a scrubber that can push the liquids down to another part of the line where the pig is retrieved along with the liquid. In smaller lines, the production is halted for periods of time to increase the formation pressure to move the accumulated fluids from the low points in the line. Additionally, in down-hole gas wells with accumulated fluids, plungers are traditionally used to convey the accumulated fluids to the surface, which is time-consuming and costly. The increase of accumulated fluids over time and breaks in production lead to lower overall gas production, inefficiencies and higher maintenance and production downtime. The fluids may also freeze in winter, causing plugging of the line and lost gas production.
Liquid is also typically conveyed in a turbulent flow, which leads to both energy inefficiencies and damage to the conduit, as described above. Additionally, non-turbulent flow of material can become turbulent over long distances, and flow-changing devices cannot be easily installed in an existing casing.
As shown from above, a need exists in the art for a system that requires low energy input in particulates conveying, reduces equipment wear, reduces product degradation and can transport materials for long distances, such as a mile and over. Further, a need exists for a system that can convey materials through dramatic high angle and vertical elevation and sharp directional changes. A need also exists for a system that can convey materials without plugging, and can further classify and mechanically dry materials during processing. A need exists to alleviate pressure in lines due to accumulated fluids. A need also exists in the art for a conveying system that can be easily installed within an existing casing in oil and gas production lines.
The instant invention is directed to a material handling system for developing a strong laminar flow of flowable material surrounded by a boundary layer flow of the same or different flowable material, such that long transport distances through dramatic elevation and directional changes can be achieved. The boundary layer flow protects the walls of the conducting conduit from assault by the conveyed material, thereby protecting both the walls of the conduit and the conveyed material. Further, this system can utilize low pressure to initiate the conduction of material, thereby dramatically reducing the operational costs of this system. This system can also operate in high pressure such as, for example, natural gas conveyance at up to and above 1,500 psi. However, this system can equally operate in low pressure gas wells and pipelines, including coal bed methane wells.
One embodiment of the instant invention includes a blower assembly, an inlet and an outlet conduit. The blower assembly supplies low pressure air to the system through the inlet, which in some preferred embodiments receives both air and the particulate material to be conveyed. The inlet is coupled to the flow developing device such that the air from the blower assembly passes into the mixing chamber.
The mixing chamber includes an outer barrel, an inner barrel and an accelerating chamber, wherein the inner barrel is disposed within the outer barrel and wherein the outer barrel is coupled to the accelerating chamber. The inner barrel of the mixing chamber can be either solid or hollow depending upon how materials are to be transported into the system. If materials are to be transported into the system entrained in air, then a solid or capped inner barrel is generally used. If materials are to be transported by an auger or screw type conveyor, then a hollow inner barrel may be utilized and the auger or screw placed within the hollow inner barrel.
Typically, the air from the blower is passed tangentially over the inlet such that the air, or air and material mixture, sets up a flow pattern that circulates and traverses the inner barrel towards the accelerating chamber. Once in the accelerating chamber, a vortex flow is developed. As the flow moves through the accelerating chamber, the flow accelerates and a boundary layer flow begins to develop. The flow mixture then travels out of the accelerating chamber into the outlet conduit which is coupled to the accelerating chamber. As the air/material mixture travels down the outlet conduit, the vortex flow transforms into a laminar flow surrounded by the boundary layer flow. The mixture is then transported the length of the outlet conduit until it reaches its destination.
In operation, this embodiment operates at pressures between 1-9 psi. One advantage of this lower pressure is that the operational costs are substantially reduced. A further advantage includes the reduction or substantial elimination of blowback problems.
In another embodiment of the instant invention, only the mixing chamber is used. Flowable materials flow into the inlet opening of the mixing chamber and set up the flow pattern, as described above. In operation, laminar and boundary layer flows are developed at low pressures, such as 1-10 psi, as well as high pressures, such as over 1,500 psi. Such high pressure systems are common in natural gas conveying lines.
In another embodiment, the inlet opening in the mixing chamber is configured so as to allow the material to enter the mixing chamber axially. Flow deflecting means is configured near the opening to deflect the incoming material into the circulating flow traversing the inner barrel, as described above. This embodiment can develop laminar and boundary layer flows from a turbulent flow, or can be used to restore an already existing substantially laminar flow.
Axial material entry is advantageous for inserting the mixing chamber into, for example, the tubing of an oil or gas well, where there may not be enough room in the existing casing to fit extra tubing for lateral entry. Axial entry mixing chambers can be attached between two segments of tubing or fitted inside existing tubing.
Additional embodiments of the instant invention are capable of transporting material flows through dramatic elevation and directional changes. One advantage of this feature is that the system can be utilized in various types of space and over varying terrain.
Embodiments of this system can be scaled to varying sizes. Advantages of varying sizes of this system include the ability to build a system in virtually any size space and allows users to more appropriately meet their needs, e.g., lower costs, lower production requirements and lower maintenance costs.
The material input into embodiments of this system are transported down the conduit pipe in a laminar flow surrounded by a boundary layer flow. An advantage of the boundary layer flow is that it protects the conduit pipe from material as it passes down the pipe and further protects the material that is being transported.
Due to high air to particle ratio in the material flow, the system can be shut down and restarted without the need to clear the lines, thereby gaining an advantage of eliminating costly maintenance and line plugging associated with traditional technologies.
Additionally, embodiments of this system do not emit combustion or chemical pollutants. At least one advantage of this feature is that the system does not adversely affect the environment.
Further, materials transported down the conduit are mechanically, not thermally dried of surface moisture. This provides the advantage of eliminating explosion hazards associated with current thermal dryers. It also surface dries materials at considerable lower energy costs than thermal dryers.
Other embodiments of the instant invention can separate different types of materials within the flow, due to the mechanics of the boundary layer and laminar flows. Accumulated water in natural gas flow lines, for instance, can be separated from the natural gas flow into the boundary layer and drained. This can increase gas production and reduce high pressure areas in the line. This can also reduce xe2x80x9cpluggingxe2x80x9d of the line due to freezing condensates. Also, flows that contain several different types of flowable materials, such as, for example, from a stripper oil well containing a mixture of oil, gas, condensate and water, can be separated by mass and/or form and collected with a separator tank.
The above and other advantages of embodiments of this invention will be apparent from the following more detailed description when taken in conjunction with the accompanying drawings. It is intended that the above advantages can be achieved separately by different aspects of the invention and that additional advantages of this invention will involve various combinations of the above independent advantages such that synergistic benefits may be obtained from combined techniques.